Special Test & Procedures Flashcards
Specular Microscopy
Used to examine the corneal endothelial cells
Ophthalmic Photography: External
Assists in documentation of abnormalities of the eye’s outer structures and abnormal eye movements
Does not use high magnification
Ophthalmic Photography: Slit Lamp
Uses camera back attached to the edit lamp to allow for high magnifications
Used to document anterior segment structures
High magnification possible
Ophthalmic Photography: Fundus Photography
May required dilation
Has an optical system for viewing the retina
Uses a light/flash system for illumination
Documents abnormalities of the posterior pole
Ophthalmic Photography: Angiography (Fluorescein Angiography)
Fluorescein dye administered intravenously
Examines the retinal circulation
Utilizes special filters to highlight the dye
Photographs taken in rapid sequence at a recorded time interval
Ophthalmic Photography: ICG (Indocyanine Green Chorioangiography)
ICG dye administered intravenously
Examines choroidal circulation
Uses special filters to highlight the dye
Photographs taken in rapid sequence at a recorded time interval
Ophthalmic Photography: Tomographic Imaging
Provides 3-D digital images of the optic nerve and/or retina
Optical coherence tomography (OCT)
Scanning laser polarimeter (SLP)
Heidelberg Retinal Tomographie (HRT)
Electrophysiologic Testing: Electroretinography (ERG)
Measures electrical response of retina after light stimulation
A-wave shows rod and cone activity
B-wave stems from Bipolar and Mueller cells
Electrophysiologic Testing: Electro-pculogram (EOG)
Tests function of the retinal pigment epithelium
Measures corneoretinal potential at different light levels
Electrophysiologic Testing: Visual Evoked Response (VER), Visual Evoked Potential (VEP)
Records a computerized electrical activity in the occipital cortex
Stimulates the retina with light flashes
Measures defects in the retina to brain nerve pathway
Electrophysiologic Testing: Multifocal Electroretinogram (mfERG)
Measures the electrical response of multiple discreet points within the central retina
Ultrasound (High frequency sound waves 8-10 MHz): B-scan
Brightness
Provides image of intraocular structures in the presence of media opacities
Delivers radiating sound waves
Effective in detecting tumors and retinal detachment
Two-dimensional image of ocular tissues
Ultrasound (High frequency sound waves 8-10 MHz): A-scan
Amplitude Delivers single beam, linear waves Contact or immersion methods One-dimensional image Measures distances between structures of the eye Calculate IOL power using axial length
Amsler Grid
Determines visual field defects in central 20 degrees
Held 12-14 inches from patient
Near correction
Good lighting
MonocularSchirmer TEst
Measures tear production
Strip of filter paper is placed in the outer lower fornix (five minutes)
With topical anesthetic and fornix swabbing, measures basic secretion
Without topical anesthetic, measures reflex tearing
Measures in millimeters
Worth Four-Dot
Subjective test used to measure fusion, diplopia or suppression.
Utilizes spectacles with one red lens and one greens lens
Presents two green lights, one red light, and one white light
Can be measured at distance or near, binocularly
With red lens over right eye and greens lens over left eye, record patient response.
Patient Response: Four lights
Indication: Normal fusion response
Patient Response: Two red lights
Suppression of left eye
Patient Response: Tree green lights
Suppression of right eye
Patient Response: Five lights
Diplopia
Hirschberg Test (corneal reflex test)
Used to determine presence of strabismus and to estimate misaligned eye’s deviation using corneal light reflexes.
Performed by shining a light in the person’s eyes and observing where the light reflects off the corneas
Light reflection: Center of both corneas
Normal ocular alignment
Light reflection: Light lands on medial aspects of cornea
Exotropia-one or both of the eyes turn outward
Light reflection: Light lands on lateral aspect of cornea
Esotropia-one or both eyes turns inward
Light reflection: Light lands on inferior aspect of cornea
Hypertropia-one eye turns upward
Light reflection: Light lands on superior aspect of cornea
Hypotropiaone eye deviates downwards in comparison to the other eye
Krimsky test
Test of binocular motor alignment that utilizes prisms to equalize the position of the corneal light reflex in the pupil
Patient instructed to fixate at distance (20 feet)
Penlight is shone at the eyes, and the position of the corneal reflex is noted
Increasing prism is placed over the deviated eye (apex of prism placed toward the deviation) until reflex is centered in the pupil
Position of the light reflex that is centered with the prism indicated the amount of deviation
The amount of the prism required to center the reflex is equal to the deviation
Maddox Rod
Used to measure misalignment of the eyes via a dissociating test; a dissociating test presents dissimilar objects for each eye to view so images cannot be fused. Because fusion is not stimulated, it will reveal both phobia and tropia.
Uses a red or white disc of high-powered cylinders running in parallel lines
The disc is placed over right eye with cylinders horizontal
The patient fixates at 20 feet (then repeat test at 13 inches)
The patient will see a vertical line and report whether it is left of the light, right of the light or through the light
If streak left of light-exotropia
If streak right of light-esotropia
If streak through light-no horizontal misalignment
Rotate the disc for cylinders to run vertically
Patient reports whether horizontal line appears above, below or through the light
If streak below light-hypertropia
If streak above light-hypodeviated (left hypertropia)
If streak through light-no vertical misalignment
Lacrimal Testing
Test designed to evaluate latency of nasolacrimal duct in the setting of tearing
Corneal Topography
AKA Photokeratoscopy or Videokeratography, utilizes an instrument (topographer) for mapping the cornea.
Measure the shape and curvature of the cornea from the center to 8-9 mm of the peripheral cornea.
Measures corneal power (steepness and flatness) and meridians of power (simulated K readings)
Depending on method and instrument utilized:
Measures the amount of corneal astigmatism
Measures corneal thickness
Shows location of a corneal defect
Displays symmetrical or asymmetrical curvature patterns
Measures corneal diameter
Irregular patterns can provide information on certain corneal pathologies.
Types of computerized corneal maps
Computerized corneal topography nomograms and individual maps use hundreds or even thousands of data points to graphically present information about the corneal surface. Different types of maps portray different data of the same corneal shape Axial Map (also called power map): measures the curvature of the cornea in diopters; it is a way to show the overall shape of the cornea, calculating curvature rather than power; colors are used to visually correspond to steepness and flatness; it is the most commonly used map. Tangential Map: Calculates the corneal curvature based on the tangent to the normal method and is used to identify corneal pathology. such as keratoconus; central tangential maps are able to show detailed patterns to reveal a more exact location of a corneal defect when compared to an axil map. Both types of maps represent measurements f corneal curvature, not the actual corneal power. Some automated corneal topographers are able to produce elevation maps (by comparing corneal curvature to a reference sphere) which are useful for determination of a keratoconic cornea.
